Connections in Taxonomy: the Barnacle Goose and Goose Barnacles
Recently, while traveling, I had the great pleasure of seeing a real animal out of medieval bestiaries: the barnacle goose.
The story of the barnacle goose — and its taxonomic counterpart, the goose barnacle — is one of my all-time favorite historical perspectives on animals. It’s ridiculous to the modern scientific reader, and yet it makes a lot of sense if you look at it right.
The barnacle goose, Branta leucopsis, lives in northern Europe. It’s a large black-and-white bird, stubby-billed, related to the Canada geese that are common in North America. It’s a migratory bird.
Now, migration can be a tricky thing to understand when your experiences are direct and localized rather than global. Medieval folks who lived in the barnacle goose’s winter territory saw adult birds, but no nests, eggs, or goslings, since those life stages occurred many hundreds of miles away from their view. Naturally, people developed explanations for this observation, and that’s where the barnacle comes in.
Throughout the world, including the winter (adult) territory of the goose, there’s another common life-form: the goose barnacle (various species in the order Pedunculata). These creatures are a couple of inches long and mostly white, with black borders at the places where feather-shaped plates of shell come together. They look kind of like goose eggs, or — more charmingly — like small geese wrapped tightly in their wings. Or at least, that’s the image that ended up in a few bestiaries.
Adding an even more delightful quirk to this tale, the barnacles’ habit of growing on driftwood led early biologists to conclude that barnacle geese grew from trees.*
And that’s how, much later, in the age of scientific taxonomy in the late 1700s and early 1800s, the goose was given the name “barnacle goose” and one species of barnacle was dubbed Lepas anatifera, which means “goose-bearer.”
*Depending on your religion’s dietary laws, the barnacle goose’s origin could have either broadened or restricted your dining options: Some Catholics decided that since the goose grew from barnacles, which came from the sea, the goose was actually fish instead of meat and could be eaten on Fridays. Some Jewish scholars, on the other hand, declared that a bird which grew from a tree was not kosher.
References:
IUCN Red List, http://www.iucnredlist.org/details/22679943/0
The Medieval Bestiary, http://bestiary.ca/beasts/beast1195.htm, http://bestiary.ca/beasts/beastgallery1195.htm
RSPB, https://www.rspb.org.uk/birds-and-wildlife/bird-and-wildlife-guides/bird-a-z/b/barnaclegoose/
Wikipedia, https://en.wikipedia.org/wiki/Barnacle_goose
